Ternary Diffusion with Two Moving Boundaries

The problem of unidirectional diffusion with 2 moving boundaries is pertinent to the study of reactions between condensed phases. The solution for binary diffusion is presented, and an eigenvector approach is outlined for the solution of the problem in a ternary diffusion system. The complete solution is given for some specific situations. Typically, the diffusion path deviates from the series of simple mixtures and tends to follow the direction of the minor eigenvector. This behavior is also true for cases where linear approximations are applicable.